Abstract
The complex perovskite lead iron niobate, Pb(Fe1/2Ta1/2)O3 (PFT), has beenstudied by neutron powder diffraction. Following collection of diffractiondata at 300 K and at 10 K, structural refinements have been carried out bymeans of the Rietveld method. A straightforward unit cell of symmetry R3m wasobtained for the 300 K structure, with the same symmetry, and a similar unitcell also obtained at the low temperature. In both cases, the iron andtitanium ions were found to be disordered over the perovskite B-sites.Furthermore, in order to obtain a good agreement with experiment at 10 K, itwas necessary to assign non-zero magnetic moments to the iron ions, thesebeing in a collinear, antiferromagnetic arrangement. This magnetic structurecan be described with reference to doubled unit cell axes. The factorsgoverning the observed structures of PFT are discussed by comparison with therelated system of Pb(Fe1/2Nb1/2)O3.
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